3D Terrain Sensing System Using Laser Range Finder with Arm-Type Movable Unit

摘要

A 3D configuration and terrain sensing is a very important function for a tracked vehicle robot to give precise information as possible for operators and to move working field efficiently. A Laser Range Finder (LRF) is widely used for the 3D sensing because it can detect wide area fast and can obtain 3D information easily. Some 3D sensing systems with the LRF have been presented in earlier studies (Hashimoto et al., 2008) (Ueda et al., 2006) (Ohno & Tadokoro, 2005). In those measurement systems, multiple LRF sensors are installed in different directions (Poppinga et al., 2008), or a LRF is mounted on a rotatable unit (Nuchter et al., 2005) (Nemoto et al., 2007). Those kinds of system still have the following problems: a. The system is going to be complex in data acquisition because of the use of multiple LRFs for the former case, b. It is difficult for both cases to do sensing more complex terrain such as valley, deep hole, or inside the gap because occlusions occur for such terrain in the sensing. In order to solve these problems, we propose a novel kind of sensing system using an arm-type sensor movable unit which is an application of robot arm. In this sensing system, a LRF is installed at the end of the arm-type movable unit. The LRF can change position and orientation in movable area of the arm unit and face at a right angle according to a variety of configuration. This system is therefore capable of avoiding occlusions for such a complex terrain and sense more accurately. A previous study (Sheh et al., 2007) have showed a similar sensing system in which a range imager has been used to construct a terrain model of stepfields; The range imager was, however, fixed at the end of a pole. Our proposed system is more flexible because the sensor can be actuated by the arm-type movable unit. We have designed and developed a prototype system of the arm-type sensor movable unit in addition to a tracked vehicle robot. In this chapter, Section 2 describes an overview of the developed tracked vehicle and sensing system as well as how to calculate 3D sensing position. Section 3 explains two major sensing methods in this system. Section 4 presents fundamental experiments which were employed to confirm a sensing ability of this system. Section 5 shows an example of 3D mapping for wide area by this system. Section 6 discusses these results.